Integrated Data Analysis of Profile Diagnostics at ASDEX Upgrade

Fischer, R.; Fuchs, C.; Kurzan, B.; Suttrop, W.; Wolfrum, E.

doi:10.13182/fst10-110

Cited by 223 publications

(274 citation statements)

References 8 publications

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“…Advances in UQ are needed on both the experimental and modeling sides, to better quantify and characterize the uncertainties in the equilibrium profiles and gradients, and then efficiently propagate these uncertainties through both power balance and turbulent transport models. On the experimental side, using techniques such as Gaussian process regression 119,120 or integrated data assessment [121][122][123][124] should be investigated more widely. For simulations, propagation of uncertainties requires a transition from single, deterministic simulations at a given point to ensembles of calculations as the default workflow.…”

Section: Discussionmentioning

confidence: 99%

“…It should also be noted that for some profiles, multiple independent diagnostics are often combined (such as Thomson scattering and electron cyclotron emission for measurements of T e profiles) to increase confidence in the final fit. In such cases, the use of integrated data assessment (IDA) techniques [121][122][123][124] can enable significantly improved estimates of profile and gradient uncertainties. Finally, in some experiments, it is possible to use small "jogs" or scans of the plasma through the diagnostic viewing locations to obtain more smoothly varying profile (and thus gradient) measurements; 125 similar results for diagnostics such as ECE can be obtained through small variations in toroidal field strength.…”

Section: B Quantifying the Uncertainty In The Local Driving Gradientmentioning

confidence: 99%

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Validation metrics for turbulent plasma transport

Holland

2016

Physics of Plasmas

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Developing accurate models of plasma dynamics is essential for confident predictive modeling of current and future fusion devices. In modern computer science and engineering, formal verification and validation processes are used to assess model accuracy and establish confidence in the predictive capabilities of a given model. This paper provides an overview of the key guiding principles and best practices for the development of validation metrics, illustrated using examples from investigations of turbulent transport in magnetically confined plasmas. Particular emphasis is given to the importance of uncertainty quantification and its inclusion within the metrics, and the need for utilizing synthetic diagnostics to enable quantitatively meaningful comparisons between simulation and experiment. As a starting point, the structure of commonly used global transport model metrics and their limitations is reviewed. An alternate approach is then presented, which focuses upon comparisons of predicted local fluxes, fluctuations, and equilibrium gradients against observation. The utility of metrics based upon these comparisons is demonstrated by applying them to gyrokinetic predictions of turbulent transport in a variety of discharges performed on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)], as part of a multi-year transport model validation activity.

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Section: Discussionmentioning

confidence: 99%

Section: B Quantifying the Uncertainty In The Local Driving Gradientmentioning

confidence: 99%

Validation metrics for turbulent plasma transport

Holland

2016

Physics of Plasmas

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“…Figure 4 shows the evolution of electron and ion temperature profiles, as well as of profiles of the electron density and plasma rotation frequency. The electron density (inferred by integrated data analysis (IDA) [20]) remains constant during the experiment while the central ion temperature and rotation (both measured by CXRS diagnostics) drop during the off-axis NBI phase, which is well explained by reduced central heating and momentum input. The impurity density, measured by CXRS (on helium, boron and nitrogen), remained low and constant during the experiments and result in an effective charge number of about 1.3, which is agreement with the measured level of Bremsstrahlung.…”

Section: Fast-ion Current Drive Studymentioning

confidence: 96%

Fast-ion transport and neutral beam current drive in ASDEX upgrade

Geiger¹,

Weiland²,

Jacobsen³

et al. 2015

Nucl. Fusion

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Abstract.The neutral beam current drive efficiency has been investigated in the ASDEX Upgrade tokamak by replacing on-axis neutral beams with tangential off-axis beams.A clear modification of the radial fast-ion profiles is observed with a fast-ion Dalpha diagnostic that measures centrally peaked profiles during on-axis injection and outwards shifted profiles during off-axis injection. Due to this change of the fast-ion population, a clear modification of the plasma current profile is predicted but not observed by a motional Stark effect diagnostic.The fast-ion transport caused by MHD activity has been studied in low collisionality discharges that exhibit strong (1,1) modes. In particular due to sawtooth crashes, significant radial redistribution of co-rotating fast-ions is observed which can very well be described by the Kadomtsev model. In addition, first tomographic reconstructions of the central 2D fast-ion velocity space in the presence of sawtooth crashes allow the investigation of the pitch dependence of the mode-imposed redistribution: A stronger redistribution of mainly co-rotating fast ions is observed than of those with smaller pitch values.

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“…Measurements of the local ELM-induced plasma density perturbations in the vicinity of the HFB diagnostic are presently not available. The evolution of the edge pedestal region during ELMs is estimated with the integrated data analysis (IDA) routine 17 . The overall results of the diagnostic measurements and data analysis are presented next.…”

Section: Diagnostic and Experimental Methods Descriptionmentioning

confidence: 99%

ICRF wave field measurements in the presence of scrape off layer turbulence on the ASDEX Upgrade tokamak (invited)

Ochoukov

Bobkov

Faugel

et al. 2016

Review of Scientific Instruments

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(Presented XXXXX; received XXXXX; accepted XXXXX; published online XXXXX) (Dates appearing here are provided by the Editorial Office) A new array of B-dot probes was installed on ASDEX Upgrade. The purpose of the new diagnostic is to study ICRF wave field distributions in the evanescent SOL plasma region on the low field side of ASDEX Upgrade. The vacuum measurements (no gas, BT = 0 T) reveal ICRF wave field measurements consistent with the profiles expected from the newly installed 3-strap ICRF antennas outside the antenna box: the shape of the toroidal distribution of both the amplitude and the phase is the same for the case of only the central straps being active, as for the case of only the side straps being active. These profiles become strongly modified during plasma operations. The modifications can be separated into two types: "Inter-ELM" and "During-ELM" periods. The phase distribution of the ICRF wave fields remains well-defined during the Inter-ELM period; however, it becomes more spread out over the entire 360 o range during ELMs. The observed modulations cannot be explained by the observed changes in the ICRF power, as monitored in the transmission line. However, they are consistent with ICRF coupling changes introduced by plasma filaments: the plasma density perturbations due to the filaments are high enough to change the nature of the fast ICRF wave field from evanescent to propagating. The coverage of the present diagnostic is being expanded to include both the low field side and the high field side probes. Additionally, a manipulator probe head is being developed to measure ICRF wave field radial profiles across the SOL region.

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Integrated Data Analysis of Profile Diagnostics at ASDEX Upgrade

Cited by 223 publications

References 8 publications

Validation metrics for turbulent plasma transport

Validation metrics for turbulent plasma transport

Fast-ion transport and neutral beam current drive in ASDEX upgrade

ICRF wave field measurements in the presence of scrape off layer turbulence on the ASDEX Upgrade tokamak (invited)

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